FIELD OF THE INVENTION
In the above-referred to co-pending applications, there is disclosed both bottle washing and lubricant compounds which can, inter alia, inhibit the stress crack formation ordinarily encountered when exposing a poly (alkylene) terephthalate article, such as a beverage bottle, to an alkaline environment. This phenomenon is well known and has been widely documented.
The development of this technology is predicated on the fact that "fatty acid" lubricants in the alkaline pH range are highly desirable in a bottling operation not only because of its ability to clean the conveyors, due to the soap generated by the interaction between a caustic neutralizing compound and the fatty acid, but also because of its ability to neutralize any excess acidity encountered during spillage of a soda pop or the like. However, it is these fatty acid lubricants which contribute to the stress cracking because of their alkalinity. To minimize this, the art taught neutralization of the fatty acid lubricants. However, neutralization, that is pH 7.0, diminishes the lubricating capabilities as well as the cleaning capabilities of these compounds. Thus, in the prior copending application solutions were sought to find a fatty acid lubricant which could inhibit the stress cracking phenomenon while still being a good lubricant and cleaner. This, initially, and in accordance with the teachings of U.S. Pat. No. 4,929,375, it was believed that by admixing a hydrophilic-substituted aromatic hydrocarbon having either an alkyl or aryl side chain, such as sodium xylene sulfonate or the like with an alkyl amine saponifying agent that there could be provided to the art a fatty acid lubricant which was highly dilutable and, therefore, highly efficacious in the lubrication of the poly (alkylene) terephthalate articles, and which was believed to inhibit stress crack formation even at a pH 7.
Then, as the technology evolved and as disclosed in the '801 patent, it was found that stress crack inhibition of PET articles actually did occur with fatty acid lubricants at pH greater than 7. Specifically, it was found that the hydrophilic substituted aromatic hydrocarbon was acting as a stress crack inhibitor in the lubricant concentrate.
Subsequently, and as disclosed and taught in the '280 patent, it was found that, at use levels, the amine was the primary stress cracking inhibitor, but which stress cracking inhibition capabilities were enhanced and buttressed by the aromatic hydrocarbon.
However, in order to be highly efficacious as a stress crack inhibiting lubricant, the dilution ratios of the concentrate could not be achieved in the manner comparable to that disclosed in the '375 patent. Thus, to date, the art has witnessed the development of a fatty acid lubricant which exhibits both excellent lubricating properties, cleaning properties and, concomitantly, inhibits stress crack formation in PET articles in an alkaline environment. Moreover, at least in a bottling operation, it is highly desirable that a lubricant be efficacious in lubricating the tracks upon which the various types of containers translate i.e. cans, glass and PET articles. The fatty acid lubricants disclosed in the above-referred to patents are efficacious in conjunction with any of these types of containers. Thus, the lubricants disclosed in the above-referred to patents are "universal" lubricants in their application to various beverage containers and their ability to inhibit the stress cracking ordinarily encountered with PET articles. However, and as noted, the dilutability of these lubricants, as the stress cracking properties has been enhanced, has diminished. Thus, it would be highly desirable to provide a "universal" fatty acid-based lubricant which could approach the dilution levels disclosed in the '375 patent.
Moreover, because of the cost of raw materials, the art has looked to alternatives for fatty acid lubricants, i.e. synthetic diamine lubricants, such as disclosed in PCT International Publication No. WO 92/130580, U.S. Pat. No. 5,062,978, and various other prior art.
These lubricants provide adequate lubricity, cleaning ability and the like, and have a much lower production cost. However, the ability of these lubricants to inhibit or minimize the stress cracking capabilities of PET articles in a alkaline environment and their corrosivity renders these lubricants suspect.
Thus, while providing high dilution capabilities, it would also be desirable to provide a synthetic diamine lubricant which is stress crack inhibiting, while being still applicable to other types of beverage containers.
It is to these purposes to which the present invention is directed.